(Solved) - Upgrade Windows 7

I presently run Windows 7 (Windows 7 Upgrade Option Program). I would like to upgrade to Windows 7 Professional, but since my existing program was a free upgrade from Vista, I am not sure if I can just upgrade to Windows 7 Professional, or will I need to purchase the "full OEM version"?

I am not planning for a free upgrade, but need to know if I can upgrade using Windows Upgrade..........I ask because I read that if there is a problem and you wish to return to prior version, you wolld possibly have to do a clean install and files on computer would likely be gone.